An excellent cyan-emitting orthosilicate phosphor for NUV-pumped white LED application

Abstract

In this paper, a cyan-emitting phosphor BLS:Ce³⁺ is reported that has a broad emission band covering both the blue and green regions of the visible spectrum, which can be used instead of two separate blue and green phosphors. The excitation peak of BLS:Ce³⁺ is located at 400 nm, which matches well with the emission light of efficient near-ultraviolet (NUV) chips. The BLS:Ce³⁺ phosphor has an internal quantum efficiency (IQE) higher than 90% at room temperature (RT) and an excellent thermal stability (a small reduction of 3% at 150 °C relative to the IQE at RT) and is environmentally robust (a small degradation of 6% occurs after aging for 1600 h at 85 °C/85% RH relative to the room-temperature IQE value). Using the BLS:Ce³⁺ phosphor, coupled only with a CaAlSiN₃:Eu²⁺ red phosphor and a 395 nm NUV chip, a NUV-based WLED with a high color rendering index of 90.6 has been achieved. Moreover, the luminous efficiency reaches as high as 32.2 lm W⁻¹, which is much better than that of the NUV-WLEDs employing three phosphors (blue, green and red).